Fuel dispensers are located at service stations and are used by consumers to dispense fuel into vehicles. The fuel dispenser is comprised of a housing that contains internal hydraulic components designed to retrieve fuel from an underground fuel-piping network. The fuel is metered inside the fuel dispenser for an accurate accounting and billing process, and the fuel is delivered to a hose and nozzle combination to be dispensed into a vehicle fuel tank. Examples of fuel dispensers in service station environments are disclosed in U.S. Pat. Nos. 6,087,954 and 6,089,284.
The fuel delivered underneath the ground in the fuel-piping network is delivered to each fuel dispenser via a branch conduit. When a particular fuel dispenser is requested to dispense fuel by a user, a signal from the fuel dispenser causes a turbine pump coupled to an underground storage tank to draw fuel from the underground storage tank. The fuel is then delivered to a main fuel piping network throughout the service station. The fuel dispenser opens a valve in the bottom of fuel dispenser thereby fluidly coupling a branch fuel piping from the fuel dispenser to the main fuel-piping conduit to dispense fuel. The fuel then enters into the branch conduit and enters into the fuel dispenser's fuel supply conduit downstream where the fuel is metered and then delivered to the vehicle. The fuel dispenser contains a fuel supply conduit for each different type of fuel since fuel dispensers often are capable of dispensing different types of fuel. The fuel dispenser, if vapor recovery equipped, also contains a vapor recovery conduit that is coupled to the ullage area of the underground storage tank to return captured vapors from a vehicle to the underground storage tank.
Since the main fuel piping conduit is located beneath the ground, the fuel dispenser's fuel supply conduit must be connected to the branch conduit to fluidly couple the fuel dispenser's fuel supply conduit and branch conduit together. For safety concerns and to meet regulatory requirements, a shear valve is placed inline to the fuel supply conduit and branch conduit so that an impact to the fuel dispenser will cause the shear valve to engage thereby cutting off the fuel supply from the branch conduit to the fuel supply conduit inside the fuel dispenser. The shear valve shuts off the fuel supply from the branch conduit so that fuel does not leak in the service station environment when the impact to the fuel dispenser causes the branch conduit and/or fuel supply conduit in the fuel dispenser to be damaged.
However, shear valves that are used in fuel dispensers that exist today may not be installed properly such that they properly engage when an impact is made to a fuel dispenser. In order for the shear valve to properly engage when a fuel dispenser is impacted, the shear valve and fuel supply piping conduit must be installed according to standard guidelines. However, due to human error in combination with incorrect installations, shear valves often do not engage properly when a fuel dispenser is impacted. Often, the fuel supply conduit and/or branch conduit is damaged and/or broken before the shear valve engages, thereby causing the possibility of fuel to leak through the damaged and/or broken conduits into the environment. This is caused by either the energy from the impact to the fuel dispenser not properly being directed to the shear valve such that the shear valve always engages or due to incorrect installation.
Therefore, there exists a need to provide a reliable and consistent system to ensure that a shear valve in a fuel dispenser engages when an impact to a fuel dispenser. A need also exists to make sure this system is fault tolerant to installations performed outside of the control of the fuel dispenser manufacturer.